Fluid distribution apparatus

ABSTRACT

This invention relates to a fluid-distribution apparatus in which one main fluid inlet flow is divided substantially equally between a number of outlets for example as the feeding of a plurality of burners on a gas turbine engine from a single fuel supply. At low total flow rates the difference in height of the various outlets can adversely effect the equality of distribution of liquid between the outlets and it is known to provide a restrictor in series with each outlet to improve the flow division between the outlets. However, where there is a large range of flow rates, the simple restrictors which are effective at low flow rates will cause a very substantial pressure loss at high flow rates. Further a simple restrictor essentially involves a passage of small cross-section which can become blocked by solid particles within the liquid. The present invention substitutes vortex chamber devices for the simple restrictors, arranged to provide a predetermined unique relation between flow rate and pressure drop to ensure effective equalization at low flow rates and to require only a moderate pressure drop at high flow rates. The vortex chamber devices further are less liable to blockage by solid particles.

This invention relates to a fluid flow distribution apparatus intendedto distribute a main fluid flow substantially equally between a numberof outlets.

It is well known that fluid flow distribution apparatus may userestrictors to equalise flow between the outlets but such apparatus hasthe disadvantage that the restrictors to produce the necessaryrestrictive effect must be of small dimensions and are thus liable toobstruction by solid particles that may be contained within the fluid.Also such restrictors involve excessive pressure drop at high flowrates.

The object of the present invention is to provide a fluid flowdistribution apparatus of comparatively small dimensions which does notinvolve flow passages of very small cross-section.

In accordance with the present invention a fluid flow distributionapparatus has a main inlet, a plurality of devices each having a vortexchamber, a tangential primary inlet to each vortex chamber, an outletfrom each vortex chamber coaxial therewith, a secondary inlet for eachvortex chamber offset from the central axis thereof, a primary manifoldconnecting the main inlet to all primary inlets, a secondary manifoldconnected to all secondary inlets, and a spring loaded check valvearranged to permit fluid flow from the main inlet to the secondarymanifold when pressure in the secondary manifold falls below pressure inthe main inlet by more than a predetermined amount.

Two embodiments of the invention will now be particularly described withreference to the accompanying drawings, in which

FIG. 1 is a longitudinal section of a vortex chamber device,

FIG. 2 is a transverse section on the line II--II of FIG. 1,

FIG. 3 is a diagram of a fuel flow distribution apparatus for agas-turbine engine incorporating a plurality of vortex devices,

FIG. 4 is a graph representing the performance of the flow distributionapparatus in accordance with the invention, and

FIG. 5 is a fragmentory developed cross-sectional view of onearrangement of orifices that feed the vortex chamber.

The vortex chamber of FIG. 1 has a body comprising three main parts 11,12 and 13 held together by bolts 14. The main inlet 15 is in the part 11and is connected from a position 16 in the part 12 to an orifice 17which opens tangentially into the periphery of the vortex chamber 19.The orifice 17 forms the primary inlet into the vortex chamber. Thevortex chamber is formed by a circular walled gap between parts 12 and13. The access opening in the part 12 for drilling the orifice 17 isclosed by a screw plug 21.

The vortex chamber 19 has its outlet formed on its central axis as bycoaxial openings 22 and 23 in the body parts 12 and 13.

The opening 22 is connected by a passage 24 in the body parts 12 and 13to an outlet 25 which is common to both openings 22 and 23.

The main inlet 15 connects to a check valve seat 26 against which amovable poppet valve element 27 is loaded by a spring 28. Fluid can flowfrom the main inlet 15 through the check valve to a chamber 29 in thebody part 12 which is coaxial with the vortex chamber 19. A number oforifices 31 form the secondary inlet to the vortex chamber and extendfrom the chamber 29 into the peripheral portion of the vortex chamber19. The orifices 31 are parallel to the central axis of the vortexchamber whereby fluid flow from the check valve 26, 27 will enter thevortex chamber without rotation about the central axis. Alternativelythe orifices 31 may have similar slight inclinations relative to thecentral axis as shown in FIG. 5 so that fluid entering the vortexchamber has a component of rotation about the central axis.

In operation of the device, fluid at low flow rates passing through themain inlet 15, flows through the passage 16 and the primary inlet 17 sothat a swirl or vortex flow is established in the chamber 19. Theresistance to fluid flow through the device at low flow rates issubstantially due to pressure difference established between theperiphery and the centre of the vortex chamber. Up to a predeterminedoverall pressure difference between the main inlet and the outlet thepressure rises steeply in relation to flow following a square lawbetween the points O and A in FIG. 4.

At the point A the check valve starts to open so that fluid enters thevortex chamber 19 through the orifices 31. The pressures in the inlet 15and in chamber 29 produce opposing forces on the valve 27 and the valvewill open when the difference of these pressures overcomes the loadingof spring 28. The difference of these pressures is particularly due topressure loss in fluid flow through the orifice 17. Thus the point A isdetermined by a predetermined flow rate of fluid through the primaryinlet into the vortex chamber.

If the orifices 31 forming the secondary inlet, are parallel to thecentral axis, the fluid entering the vortex chamber from orifices 31will be without rotation. Alternatively if the orifices 31 are inclinedthen entry of fluid into the vortex chamber will include a certaindegree of rotation. With increase in the flow rate through orifices 31and the swirling effect produced wholly or in part by the flow from theprimary inlet, the pressure difference across the vortex will vary independence on the total flow rate. The unbroken line in FIG. 4 betweenpoints A and B shows the relation between the overall pressuredifference between inlet and outlet and the total flow rate that couldbe obtained with the device as shown in FIGS. 1 and 2. In particular itwill be noted that between the points A and B the line approximates to astraight line. Different arrangements of the primary and secondaryinlets and of the check valve may be arranged to produce other relationseither linear or non linear between total flow and overall pressuredifference. The broken line in FIG. 4 illustrates the relation betweenthe overall pressure difference and total flow that would take place inthe device if there were no vortex flow in the vortex chamber.

In designing the device in accordance with the invention the relationbetween overall pressure difference and total flow will be dependent onthe pressure loading of the check valve, the dimensions of the vortexchamber and more particularly the radial positions of the secondaryinlets and their arrangement so as to enter the vortex chamber eitherwith or without rotation. It is necessary for the secondary inlets to beoffset from the central axis firstly in order to avoid the possibilitythat secondary flow may pass directly to the outlet when entering thevortex and secondly to enable a pair of outlets to be provided onopposite sides of the vortex chamber at the central axis.

The distribution apparatus shown in FIG. 3 is intended particularly foruse with distribution of fuel to a gas-turbine engine. The main inlet 41has one branch 42 leading to a primary manifold 43 and another branch 44with a check valve 45 therein leading to a secondary manifold 46. Themanifolds 43 and 46 are only partly shown and will connect to severalassociated vortex chamber devices. Each such device comprises a vortexchamber 47 having a tangential primary inlet supplied by a branch 48 ofthe primary manifold 43 and a secondary inlet supplied by a branch 49from the secondary manifold 46. The vortex chamber 47 has two opposedcoaxial outlets which supply fuel to two vapourising tubes 51 and 52leading to the engine combustion chambers.

Each vortex chamber device in FIG. 3 in combination with check valve 45operates substantially as described with reference to FIGS. 1 and 2 toproduce a pressure difference between the main inlet 41 and the outletsof each vortex chamber device, the pressure difference at quite low flowrates being arranged to be substantially greater than the pressure headof fuel between the upper and lower vapourising tubes. In this way flowsto the vapourising tubes are substantially equalised.

In the illustrated embodiments the check valve is caused to open whenthere is sufficient pressure drop in the orifice forming the primaryinlet. The pressure drop available for opening the check valve asillustrated will be increased if the orifices forming the secondaryinlets are located between the centre and the periphery of the vortexchamber. The check valve shown in the illustrated embodiments may besubstituted by any other valve means which can be arranged to remainclosed at low total flow rates and to open at high total flow rates. Themethod of controlling the valve preferably involves the use of apressure drop dependent on flow rate through the device. For example thevalve means may comprise a piston valve which whilst being openable toconnect flow from the main inlet to the chamber 29 will not respond topressure within the chamber 29. The pressure difference for opening sucha valve may then be connected from any suitable points of the devicesuch for example as the main inlet 15 and the outlet 25.

A fluid distribution device according to the invention may be quitecompact and light in weight having regard to the restricting effect thatit produces on the flow of fluid. Further such a fluid distributiondevice does not involve the use of small orifices.

I claim:
 1. A fluid flow distribution apparatus having a main inlet, aplurality of devices each having a .Iadd.circular .Iaddend.vortexchamber, a tangential primary inlet to each vortex chamber, .[.an.]..Iadd.a coaxial .Iaddend.outlet from each vortex chamber .[.coaxialtherewith, a.]. .Iadd.at least one .Iaddend.secondary inlet for eachvortex chamber .[.offset from the central axis thereof.]. .Iadd.in theperipheral portion thereof parallel or nearly parallel to the vortexchamber axis, .Iaddend.a primary manifold connecting the main inlet toall primary inlets, a secondary manifold connected to all secondaryinlets, and a spring loaded check valve arranged to permit flow from themain inlet to the secondary manifold when pressure in the .Iadd.maininlet exceeds pressure in the .Iaddend.secondary manifold .[.falls belowpressure in the main inlet.]. by more than a predetermined amount.
 2. Afluid flow distribution apparatus as claimed in claim 1 wherein eachsecondary inlet is arranged so that liquid may enter the associatedvortex chamber therefrom with rotation about the central axis thereof.3. A fluid flow distribution apparatus as claimed in claim 1 whereineach vortex chamber includes two separate outlets each coaxial with thevortex chamber and oppositely directed.